Φ-measure and Disoriented chiral condensates

Fluctuations in the ratio of neutral to charged pions arising due to formation of disoriented chiral condensates (DCC) are discussed using the Φ-measure. The properties of the measure for various cases of DCC and non-DCC are discussed. The effect of detector efficiencies and other experimental factors are presented. Application of the Φ-measure to simulated data, within the context of a simple DCC model are also discussed. In heavy-ion collisions, there is rapid expansion of collision debris along the longitudinal direction, leading to supercooling of the interior interaction region. This may result in the formation of domains of unconventionally oriented vacuum configurations as allowed by chiral symmetry called as disoriented chiral condensates (DCC) [1]. Detection of these would provide important informations on the vacuum structure of the strong interaction and the nature of chiral phase transition. To have a system in which chiral symmetry is restored in the laboratory and to be able to study the above features is one of the main goals of ultra-relativistic heavy-ion collision experiments. It has been predicted that DCC formation is associated with large event-byevent fluctuations in the neutral to charged pion ratio. The probability of the neutral pion fraction [2,3], f , is